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Reconciliation of Gross Unrecognized Tax Benefits (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Income Tax Contingency [Line Items]      
Balance at beginning period $ 53 $ 41 $ 44
Decrease related to expiration of statute of limitations (13) (8) (3)
Increase (decrease) related to prior years tax positions 13 15 (7)
Increases related to current year tax positions 6 5 7
Decreases related to settlements (13)    
Balance at end of period $ 46 $ 53 $ 41